Andy Webster's future at Rangers is in doubt as Hearts have refused to authorise his registration.
Hearts have contacted the Scottish Football Association with their concerns about the loan of Webster from Wigan to Rangers.
Webster left Hearts under a cloud last summer after envoking article 17 of FIFA's regulations which permitted him to walk out 12 months before the end of a four-year contract, providing he moved to another country.
The Scottish international struggled to make an impact at Wigan and they allowed him to move on loan to Rangers last week.
However, the move has been thrown into doubt because Hearts still hold Webster's registration and the Tynecastle outfit claim the defender should not be allowed to join Rangers until his original contract with hearts expires.
The SFA have passed on the matter to Fifa who are set to make a final decision on whether or not Webster can play for Rangers this season.
The SFA confirmed: "We are unable to register Andy Webster for Rangers as he is already registered at Hearts. The matter has been passed to Fifa."